# GTU Question Paper Digital Logic Design ECE III SEM May 2011

GUJARAT TECHNOLOGICAL UNIVERSITY

B.E. Sem-III Remedial Examination May 2011

Subject code: 130701

Subject Name: Digital Logic Design

Total Marks: 70

Instructions:

1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

(i)   Draw symbol and construct the truth table for three input Ex-OR gate.

(ii)   What is the principle of Duality Theorem?

(iii)   Explain briefly: standard SOP and POS forms.

(iv)   What are Minterms and Maxterms?

(v)  Define: Noise margin , Propagation delay

(vi)   Give comparison between combinational and Sequential logic circuits

(vii)   What is race-around condition in JK flip-flop?

Q.2 (a) (i) Explain NAND and NOR as an universal gates

(ii) Convert decimal 225.225 to binary ,octal and hexadecimal

(b) (i) Implement Boolean expression for Ex-OR gate using NAND gates only

(ii) convert decimal 8620 into BCD , excess-3 code and Gray code.

OR

(b) (i) Simplify the following Boolean function using K-map

F( w,x,y,z) = £( 1 , 3 , 7 , 11 , 15 )

with don’t care conditions d( w,x,y,z ) = £( 0, 2 ,5 )

(ii) Draw logic diagram , graphical symbol , and

Characteristic table for clocked D flip-flop

Q.3 (a) Design a combinational circuit whose input is four bit binary number and output is the 2’scomplement of the input binary number.

OR

Q.3 (a) Design a BCD to decimal decoder

(b) What is multiplexer? Implement the following function with a multiplexer:                  F(A,B,C,D) = (0 , 1 , 3 , 4 , 8 , 9 ,15 )

Q.4 (a) Write short note on : Read Only Memory (ROM)

(b) A combinational circuit is defined by functions:

F1(A,B,C) = ( 3 , 5 , 6, 7 )

F2(A,B,C) = £( 0 , 2 , 4, 7 )

Implement the circuit with PLA having three inputs four product term and two outputs

OR

Q.4 (a) Give classification of counters and explain asynchronous

4-bit binary ripple counter

(b) Explain briefly:

(i)   logic and shift micro-operations

(ii)   fixed-point binary data and floating-point data

Q.5 (a) Draw block diagram of a 4-bit arithmetic logic unit. Design an 07 adder/subtractor circuit with one selection variable S and two inputs A and B .when S = 0 circuit performs A+B, when S = 1 circuit performs A – B by taking the 2’s complement of B

(b) Draw and explain block diagram of microprograme control.                                       07

OR

Q.5 (a) Simplify the following Boolean function using tabulation Method and 07 draw logic diagram

using NOR gates only F(w,x,y,z ) = ( 0 ,1 , 2 , 8 ,10 ,11,14,15 )

(b) Explain working of master-slave JK flip-flop with necessary logic diagram 07 , state equation and state diagram.